The present invention relates to an information processing apparatus for controlling memory requests during operation of an information processor.
Control of memory requests in the operation of an information processing apparatus may be accomplished, using a system of MOVE instructions by which data on a memory indicated by a first operand, are transferred byte by byte to a storage location on another memory, indicated by a second operand. In the execution of these MOVE instructions, the actual transfer of data takes place a plurality of bytes at a time, in order to improve the performance of the information processing apparatus.
In such a system, the presence or absence of destructive overlap between the two operands is detected according to the difference between the leading address of the first operand and that of the second operand. In response to the detection of operand overlap, a read address for the control memory is generated corresponding to the extent of the overlap lag, and an address, which references the control memory in order to determine which step to be executed next, is altered to demand memory access accordingly.
As an example of such a system by the prior art, reference may be made to the U.S. Pat. No. 4,652,991, which discloses a system having a calculating unit for calculating the difference between addresses from the transfer originating side address storing unit and addresses from the transfer receiving side address storing to calculate the duplication lag between the effective address of the transfer originating side data and that of the transfer receiving side data and thereby calculating the difference between the transfer originating side data and the transfer receiving side data. In this calculating operation, the address difference is calculated by the calculating unit after the addresses are stored into the address storing unit. For this reason, an information processing apparatus capable of generating the address of operand data by address qualification, such as base qualification or index qualification, can calculate the difference between the transfer originating side data and the transfer receiving side data only after subjecting both data to address qualification and generating effective addresses.